The major thing to understand about hip-hop is that it's not about theory, it's a way of life. Five elements blended together to form a culture that values knowledge, self-expression, etc.

Rap/breaks/DJing came about because inner city schools cut out music programs across the board, and as most of those families could not afford instruments, they began to "make their own" by utilizing a record player AS their instrument. By capturing beats, breakdowns, snippets of music, they created a patchwork quilt of sound that meshed together to form rudimentary beat and bass driven music that was extremely danceable, and lended itself quite well to a party atmosphere. It wasn't until Melly Mel dropped "The Message" and Kool Moe Dee destroyed Busy Bee Starsky that the real MC began to become the voice of the people who no longer had one of their own.

They took poetry, so they created their own, with their own language, linguistic elements, style, cadence, flow. Over time, they were able to break down rhythmic word play, metaphorical content, simile, punchline jokes, etc, into a 8-16 bar format, which is where that expression in urban usage comes from.

The beautiful thing about this culture is its realization that music has no color, despite its origins, and that good production work is not just "copy pasting someone elses music."

I think it says something about how deep real hiphop can actually penetrate into the mainstream, to even people like Mobius who doesn't necessarily like every part of the genre, but can appreciate some forms of it.

Also, on topic: Billy Connolly nails it.